image-size = 20px;
/*
 * 划词翻译按钮样式
 */
#translate-button
    width: image-size;
    height: image-size;
    padding: 0.4%;
    margin: 0;
    position: fixed;          
    display: none;
    box-shadow: 0px 0px 2px 2px #ddd;
    cursor: pointer;
    border-radius: 50%;
    z-index: 2147483648;
    box-sizing: content-box;
    overflow: hidden;
    transition: box-shadow 200ms ease-in-out,transform 300ms ease; // set transtition effect when hover occurs
    animation: fade-in 300ms ease-in-out; // set fade-in animation on selection icon

    &&:hover    
        box-shadow: 0px 0px 8px 3px #bbb;  
        transform: rotate(180deg);   
    
    img
        width: image-size;
        height: image-size;
        padding: 0;
        border: 0; 
        margin: 0;    
        vertical-align: top; // fix the style problem in some websites                      
               
    
    @keyframes fade-in{  
        0%{ opacity: 0;}
        100%{ opacity: 1;}
    }